This study has as its objective, the study of intracellular function in the guinea pig organ of Corti. Single cells, both inner and outer hair cells and non-sensory cells, will be punctured by microelectrode and their performance in the absence and presence of sound stimulation will be measured. The electrophysiological parameters of cochlear microphonic, resting membrane potential, and receptor potentials will provide tuning curve information on the mechanical motion of the basilar membrane and on the activity of, or spread of electrical activity into non-sensory cells. Inner hair cells will be tested to determine if they respond to the velocity component of basilar membrane motion and as to whether or not their tuning is affected by electrically induced activity of the crossed olivocochlear efferent nervous system. After ototoxic drug treatment, similar measurements will again be made to determine if electrically measurable ototoxic effects correlate with known morphological changes and if the non-sensory cells have a role in the sensory epithelium degeneration. Procion or lucifer electrophoretic dye marking will be followed by histological procedures to identify the recorded cells.